Hydrocotyle americana (American Water Pennywort)

Plant Info
Also known as: American Marsh-pennywort
Genus:Hydrocotyle
Family:Araliaceae (Ginseng)
Life cycle:perennial
Origin:native
Status:
  • State Special Concern
Habitat:shade, sun; marshes, swamps, forest floodplains, seeps
Bloom season:May - August
Plant height:2 to 10 inches
Wetland Indicator Status:GP: none MW: OBL NCNE: OBL
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 5-petals Cluster type: flat

[photo of flowers] Flowers are 1/16 to 1/8 inch across with 5 small white to green petals and 5 stamens. Up to 7 star-shaped, nearly stalkless flowers are clustered the leaf axils forming unbranched clusters (umbels).

Leaves and stems: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of leaves] Leaves are round to kidney-shaped, ¼ to 2¼ inches wide, with 6 to 10 shallowly toothed, shallow lobes around the edge, on a sparsely hairy stalk up to 2 inches long. New leaves may have a few sparse hairs on the surface that quickly wear away. Stems are hairless, slender and creep along the ground, rooting at the nodes and often creating small but dense colonies.

Fruit: Fruit type: seed without plume

Fruit is tiny, dry, flattened, and circular, containing two seeds that split apart.

Notes:

Formerly in the Apiaceae (carrot) family, American Water Pennywort was listed as a Special Concern species for MN in 1984 due to its few numbers in the state and specialized habitat, which, according to the DNR, is primarily along cold groundwater streams and seeps within larger river valleys. A relatively common species in Wisconsin, Minnesota is the extreme western edge of its range. Similar is Hydrocotyle ranunculoides (Floating Marsh Pennywort), which is primarily a more southern, eastern and Pacific coast species with a disjunct population known to be in Scott County. H. ranunculoides is more often found floating in shallow water, it has more deeply lobed leaves than H. americana, and its flower clusters are on a stalk up to 3 inches long arising from the leaf node, where the flower clusters of H. americana are stalkless or nearly so.

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More photos

Photos by K. Chayka, Peter M. Dziuk and John Thayer taken at William O'Brien State Park.

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